For your privacy, your screen and audio recordings are stored locally and NEVER leave your Mac. If you choose to use our meeting summarization or Ask Rewind features, only relevant text-based data is sent to the cloud. We do compression and Automated Speech Recognition (ASR) all locally on your Mac. Learn more.

While running Rewind you can open Activity Monitor search for "rewind" and switch to the "Network" tab:

The only traffic you should expect is documented here.